Rainbow trout cell bioassay-derived relative potencies for halogenated aromatic hydrocarbons: Comparison and sensitivity analysis

Rainbow trout hepatoma cells, stably transfected with a luciferase reporter gene under control of dioxin-responsive elements (RLT 2.0 cells) were used to derive relative potencies (RPs) for a variety of halogenated aromatic h ydrocarbons (HAHs) that are structurally similar to 2,3,7,8-tetrachlorodibe nzo-p-dioxin (TCDD). This in vitro bioassay utilizes 96-well microplates, w hich provide high sample throughput and assay efficiency without affecting sensitivity. The RLT 2.0-derived potencies for dioxin and furan congeners, relative to 2,3,7,g-TCDD, ranged from 0.917 for 1,2,3,4,7,8-hexachlorodiben zofuran to 0.208 for 1,2,3,7,8-pentachlorodibenzofuran. All mono- and di-or tho polychlorinated biphenyls (PCBs) tested had RPs that were orders of mag nitude less than TCDD, but point estimates could not be determined. The RLT 2.0-derived RPs were found to be comparable to both other rainbow trout-sp ecific RPs and RPs based on mammalian bioassays. Sensitivity analysis sugge sted that the range of uncertainty associated with TCDD equivalent (TEQ) es timates based on RLT 2.0-derived RPs is approximately 10-fold. Within this degree of uncertainty and the context of this study, the RLT 2.0 bioassay s howed no definitive biases or inaccuracies relative to similar mammalian- o r fish-specific in vitro bioassays. Thus, the RLT 2.0 bioassay appears to b e a useful tool for evaluating dioxinlike potency of HAHs to fish.